Blood products such as albumin or clotting factors are prepared from large numbers (up to about 20,000) of pooled blood donations. A sizable portion of the contributors to these large pools of blood are probably carriers of pathogenic viruses (e.g., hepatitis, Epstein-Barr, and cytomegalovirus). For most patients the occasional exposure to a virus-contaminated blood product is probably inconsequential. However, the risk is substantial for immunosuppressed patients and patients who are exposed to these products over prolonged periods of time.
One patient group that is considered at risk for being regularly exposed to human blood products are hemophiliacs. There are approximately 40,000 hemophiliacs in the United States and in western Europe who are regularly treated with preparations of factor VIII, a product of blood.
Three precautions are routinely taken by blood collection centers to identify and eliminate blood donations from carriers of pathogenic viruses: (1) Each unit is tested for the presence of hepatitis B antigen; (2) Each unit is tested for antibodies against HIV; and (3) The prospective donor is asked to voluntarily disclose risk factors. The shortcomings of the voluntary disclosure statement are obvious. They are underscored by the high frequency of acquired immunodeficiency syndrome (AIDS) among hemophiliacs who are regularly treated with factor VIII isolated from pooled human blood.
Screening procedures for most viruses may become available, in the future. However, with some viruses, such as HIV, there is a lag phase in which a recently infected donor will test negative although he is infectious. Viruses also can mutate and thus escape immunologic detection systems. Furthermore, to systematically reject as blood donors all identifiable carriers of pathogenic viruses may not be practical because it could severely restrict the donor pool.
In addition to being able to inactivate viruses in soluble blood products, such as albumin and clotting factors, it would be useful to have a method of inactivating viruses in whole blood and cellular blood products, such as red cells, bone marrow cells.
Heat treatments, extraction of virus with solvents and detergents, and treatment with high doses of gamma radiation can be effective means of inactivating viruses. However, since those procedures are rigorous and nonspecific their applicability is limited.